Electrical submersible pumps (ESP) are often employed to pump well fluid from wells. A typical ESP includes a rotary pump driven by an electrical motor. Normally, the ESP is suspended in the well on a string of production tubing. A seal section, usually located between the motor and the pump, has a movable element to reduce a pressure differential between the well fluid exterior of the motor and motor lubricant contained in the motor. The pump may be a centrifugal pump having a plurality of stages, each stage having an impeller and a diffuser.
ESP motors are typically supplied electrical power from a motor lead and power cable extending to the wellhead. In one type, the motor lead has a connector, often called a pothead, on its lower end. The receptacle on the motor head includes a base with a plug opening extending into the motor head. A terminal block is mounted within the plug opening. The motor lead connector or plug has a nose portion that inserts into the plug opening. Electrical terminals in the plug protrude from the plug and engage electrical terminals of the terminal block. The motor lead plug has a flange that abuts the base formed on the motor head. Screws or bolts extend through the flange into threaded holes in the base to secure the plug to the motor head.
The threaded bolt holes in the base limit the amount of cross sectional space of the plug opening, which may be circular or oblong. In some cases, more space for the electrical terminals than is available in the plug opening would be desirable. For example, with motors having higher voltage and current ratings, and/or higher temperature ratings, the limited space available in the plug and plug opening may limit the capability of the motor. Also, some motor leads and plugs have auxiliary lines, such as instrument wires or fiber optic lines, in addition to the power conductors. The auxiliary lines require additional space in the plug and plug opening.